Don't attempt logging in on a PREAUTH connection

Node-imap already correctly recorded state for PREAUTH connections,
but attempted to login anyway, which results in a timeout, as it waits
for the connection to get into a state it can never reach.
Add isConnected and isAuthenticated properties
Fix re-IDLE
Merge pull request #109 from antifuchs/fix-preauth-connections

Don't attempt logging in on a PREAUTH connection
fix style
Add UTF-7 support where needed for mailbox names
Fix variable case
Bump version
try to be a bit clearer about where the extra gmail properties are stored
fix typo
fix one last typo
fetch() rewrite
partial update for readme post-fetch() rewrite
Remove obsolete helper module
Fix 'struct' default for fetch()
Check for boolean true in headers.fields for fetch()
Update more documentation to reflect fetch() rewrite
remove example
rename is* connection properties
use util.isDate instead of instanceof